Answers to the “Do I Know This Already” Quizzes and

50 Pages·2015·0.38 MB·English

APPENDIX A
Answers to the “Do I Know
This Already” Quizzes and
“Review Questions”
Answers to the “Do I Know This Already” Quizzes
Chapter 1
1. A. Explanation: Fedora is an experimental/enthusiast version containing
many components that may or may not make it into the RHEL distribu-
tion tree and onto the exams.
2. D. Explanation: All RHEL software updates are made available in CentOS
as well.
3. A. Explanation: In particular, in Chapter 10, “Working with Virtual
Machines,” you’ll be happy to have a GUI at your disposal.
4. C. Explanation: XFS is used as the default file system. When Red Hat
decided which file system to use as the default file system, Btrfs was not
stable enough yet.
5. A. Explanation: The size of an XFS file system cannot be reduced.
6. C. Explanation: The Fedora project tries to make a stable distribution as
well. There are many Fedora users around the globe who use Fedora as a
production distribution.
7. D. Explanation: The Troubleshoot an Existing Installation option is avail-
able when booting from disk, not on the Installation Summary screen.
8. D. Explanation: You are allowed to use an unsecure password; you just
have to confirm it twice.
9. D. Explanation: Language settings can be changed after installation. This
is done easily through the Settings option in the graphical interface.
10. B. Explanation: Even if it makes sense having /home on a dedicated parti-
tion, this is not part of a default installation.
4 Red Hat RHCSA/RHCE 7 Cert Guide
Chapter 2
1. B. Explanation: Answer B shows the correct syntax. The 2 redirects error mes-
sages, and &1 makes sure that the same is done for STDOUT.
2. A and B. Explanation: /etc/profile is the file that is processed for all users who
are starting a login shell.
3. C. Explanation: On Linux, the current directory is not set in the PATH
variable.
4. D. Explanation: A pipe is used to process the output of the first command and
use it as input of the second command.
5. A. Explanation: The command history -c removes the in-memory state from
the history file of current history. Remove ~/.bash_history also to make sure
that all history is removed.
6. D. Explanation: Ctrl+X is not a valid history command.
7. D. Explanation: Bash completion works for commands, files, and variables and
other names if configuration for that has been added (like hostnames for the
SSH command).
8. A. Explanation: You need the command :%s/old/new/ to replace all instances
of old with new. % means that it must be applied on the entire file. s stands for
substitute. The g option is used to not apply the command to only the first
occurrence in a line (which is the default behavior) but on all occurrences.
9. B. Explanation: The /etc/motd file contains messages that are displayed after
user login on a terminal session.
10. C. Explanation: The man -k command goes through a database to find the
keywords you are looking for. On RHEL 7, this database is updated with the
mandb command. The previously used makewhatis command is removed
from RHEL 7.
Chapter 3
1. D. Explanation: Program files that are not required to boot a system are typi-
cally stored in a subdirectory below the /usr directory.
2. C. Explanation: The /var directory is used on Linux to store files that may
grow unexpectedly.
3. A. Explanation: The /etc/directory contains configuration files that are needed
while your server boots. Putting /etc on a dedicated device would make your
server unbootable.
4. C. Explanation: The df -h command shows mounted devices and the amount
of disk space currently in use on these devices. The -T option helps in
Appendix A: Answers to the “Do I Know This Already” Quizzes and “Review Questions” 5
recognizing real file systems (as opposed to kernel interfaces) because it shows
the file system type as well.
5. C. Explanation: The option -a shows hidden files, -l gives a long listing, -t
sorts on modification time which by default shows newest files first, and -r
reverts the sorting so that newest files are shown last.
6. C. Explanation: To copy hidden files as well as regular files, you need to put a
. after the name of the directory the files are in. Answer A copies hidden files
as well, but it creates a subdirectory $USER in the current directory.
7. A. Explanation: The mv command enables you to move files but also to
rename files.
8. D. Explanation: In hard links, no difference exists between the first and subse-
quent hard links.
9. C. Explanation: The option -s is used to create a symbolic link. While creating
a link, you first have to specify the source, and next you specify the destination.
10. C. Explanation: Use the option -r to add one single file to an archive you have
created with tar.
Chapter 4
1. A. Explanation: The head command by default shows the first 10 lines in a
text file.
2. D. Explanation: The wc command shows the number of lines, words, and
characters in a file.
3. D. Explanation: When using less, the G key brings you to the end of the cur-
rent file.
4. A. Explanation: The -d option is used to specify the field delimiter that needs
to be used to distinguish different fields in files while using cut.
5. A . Explanation: The sort command can sort files or command output based
on specific keys. If no specific key is mentioned, sorting happens based on
fields. The option -k3 will therefore sort the third field in the output of the
ps aux command.
6. D. Explanation: When used in a regular expression, the ^ sign in front of the
text you are looking for indicates that the text has to be at the beginning of the
line.
7. A. Explanation: The ? regular expression is used to refer to zero or one of the
previous characters. This makes the previous character optional, which can
be useful. If the regular expression is ‘colou?r’, for example, you would get a
match on ‘color’ as well as ‘colour’.
6 Red Hat RHCSA/RHCE 7 Cert Guide
8. B. Explanation: The . is used as a regular expression to refer to any single
character.
9. D. Explanation: The awk command first needs to know which field separator
should be used. This is specified with the -F : option. Then, it needs to specify
a string that it should look for, which is /user/. To indicate that the fourth
field of a matching file should be printed, you need to include the { print $4 }
command.
10. B. Explanation: Use grep -v to exclude lines containing the regular expression
from the results.
Chapter 5
1. B. Explanation: The console is the screen you are working from. On the con-
sole, a terminal is started as the working environment. In the terminal, a shell
is operational to interpret the commands you are typing.
2. A. Explanation: The console is the screen you are working from. On the con-
sole, a terminal is started as the working environment. In the terminal, a shell
is operational to interpret the commands you are typing.
3. C. Explanation: The console is the screen you are working from. On the con-
sole, a terminal is started as the working environment. In the terminal, a shell
is operational to interpret the commands you are typing.
4. B. Explanation: The six virtual consoles that are available on Linux by default
are numbered /dev/tty1 through /dev/tty6. The device /dev/pts/6 is used to
refer to the sixth pseudo terminal, which is created by opening six terminal
windows in a graphical environment.
5. A and C. Explanation: A pseudo terminal device is created when opening new
terminals using SSH or from the graphical interface.
6. D. Explanation: Typically, a server reboot is only necessary after making
changes to the kernel and kernel modules that are in use. Changing the net-
work configuration does not normally require a reboot, because it is possible
to just restart the network service.
7. C. Explanation: Windows has no native support for SSH. You need to install
PuTTY or similar software to remotely connect to Linux using SSH.
8. D. Explanation: Key fingerprints of hosts that you have previously connected
to are stored in your home directory, in the subdirectory .ssh in a file with the
name known_hosts.
9. C. Explanation: The ForwardX11 option in the /etc/ssh/ssh_config file
enables support for graphical applications through SSH.
Appendix A: Answers to the “Do I Know This Already” Quizzes and “Review Questions” 7
10. C. Explanation: To initiate key-based remote authentication, you should copy
the public key to the remote server. The most convenient way to do so is using
the ssh-copy-id command.
Chapter 6
1. C. Explanation: Privileged users are opposed to unprivileged users. A privi-
leged user can execute tasks in kernel space, without any further restriction. By
default, only the user root exists as privileged user.
2. D. Explanation: In the sudo configuration file, all members of the group wheel
by default get access to all administrator tasks.
3. B. Explanation: The runas command does not exist on Linux.
4. B. Explanation: The hashed user passwords are stored in /etc/shadow.
5. C. Explanation: The file /etc/default/useradd is read for default settings when
new user accounts are created.
6. A. Explanation: The chage command enables you for managing password
properties.
7. B. Explanation: There is no file /etc/.profile.
8. C. Explanation: Security was not a goal in the original design of LDAP, and
has to be applied separately.
9. A. Explanation: The system-config-authentication tool was used in RHEL 6
and no longer exists in RHEL7. It has been replaced with authconfig, which
comes in a command-line version, a TUI (text user interface) version, and a
GTK (graphical) version.
10. D. Explanation: Unprivileged users should be able to set up LDAP authentica-
tion, which is why no admin name is needed to configure LDAP login.
Chapter 7
1. C. Explanation: The newgrp command is used to set the effective primary
group, which will effect default group ownership on new files until the current
shell session is ended. The chgrp command is used to set the group owner of
an existing file. Chgrp is not related to any user account and it affects newly
created files only.
2. A. Explanation: The find / -user linda command searches all files that are
owned by user linda. Notice that find also has a -uid option that allows you to
locate files based on a specific UID setting. This does not allow you to search
files based on a username, but it will let you find files based on the UID of a
specific user.
8 Red Hat RHCSA/RHCE 7 Cert Guide
3. C. Explanation: chgrp myfile sales does not set group ownership for the file
myfile. The order in this command is wrong; chgrp first needs the name of
the group, followed by the name of the owner that needs to be set.
4. C. Explanation: When used in relative mode, the three digits are used to spec-
ify user, group, and others permissions. The value 6 is used to apply read and
write.
5. C. Explanation: The chmod g+s /dir command adds (+) the SGID permis-
sion to /dir. Answer A (chmod u+s) adds SUID to the directory, with chmod
g-s the SGID permission would be removed, and the 1 in chmod 1770 /dir
would set sticky bit and not SGID.
6. D. Explanation: ACL support is not offered by default on all file systems. If
you get an “operation not supported” error message, make sure to add the acl
mount option and remount the file system.
7. B. Explanation: Although answers A and B will both set default ACLs, answer
B is better because it adds x to the permissions. Without x, members of the
group sales will have no way to enter the directory using the cd command.
8. A. Explanation: The umask is a systemwide setting and cannot be used to
apply to specific directories only. Use a default ACL as shown in answer A to
perform this task.
9. C. Explanation: In a umask, 0 in the first position gives all permissions to the
file owner. 2 in the second position ensures that members of the group owner
can read files, and 7 in the third position takes away all permissions for others.
10. C. Explanation: The lsattr command shows current attribute settings to files.
The ls command is not capable of showing file attributes, and the other com-
mands that are mentioned do not exist.
Chapter 8
1. D. Explanation: Based on the /27 subnet mask, the networks are 192.168.4.0,
192.168.4.64, 192.168.4.128, and 192.168.4.192. That means that IP addresses
II, III, and IV belong to the same network.
2. B. Explanation: The 169.254.0.0 network address does not belong to the pri-
vate address ranges, which are 10.0.0.0/8, 172.168.0.0/12, and 192.168.0.0/16.
3. C. Explanation: By default, the network device names are based on the device
type, location, and identification.
4. D. Explanation: Use of the ifconfig command is deprecated; use the ip com-
mand instead. The ip addr show command shows information about the state
of the interface as well as the current IP address assignment.
5. A. Explanation: The network service should not be used anymore in RHEL 7.
Appendix A: Answers to the “Do I Know This Already” Quizzes and “Review Questions” 9
6. B. Explanation: The nmcli-examples man page was created to make working
with the long commands in nmcli a bit easier.
7. C. Explanation: On RHEL 7, nmtui is the default utility to set and modify the
network interface. Notice that RHEL 7 does not have system-config utilities
anymore for configuring networking that were available in earlier versions of
RHEL.
8. D. Explanation: When the connection is added, you use ip4 and gw4 without
a V.
9. A. Explanation: You should not set the DNS servers directly in /etc/resolv.
conf, because the /etc/resolv.conf file is automatically written by the Network-
Manager service.
10. C. Explanation: The name of the configuration file that contains the hostname
is /etc/hostname. Notice that on earlier versions of RHEL the file /etc/
sysconfig/network was used for this purpose.
Chapter 9
1. B and D. Explanation: There are two different types of processes that each
request a different management approach. These are shell jobs and daemons.
A cron job and a thread are subdivisions of these generic categories.
2. B. Explanation: The Ctrl+Z command temporarily freezes a current job, after
which the bg command can be used to resume that job in the background.
3. A. Explanation: The Ctrl+C command cancels the current job. Ctrl+D sends
the EOF character to the current job, which can result in a stop if this allows
the job to complete properly. The difference with Ctrl+C is that when using
Ctrl+C the job is canceled with no regard to what it was doing. The Ctrl+Z
keystroke freezes the job.
4. A and B. Explanation: Individual threads cannot be managed by an administra-
tor. Using threads makes working in a multi-CPU environment more efficient
because one process cannot be running on multiple CPUs simultaneously,
unless the process is using threads.
5. A. Explanation: The ps ef command shows all processes, including the exact
command that was used to start them.
6. C. Explanation: To increase process priority, you need a negative nice value.
-20 is the lowest value that can be used.
7. C. Explanation: Use the renice command to change priority for currently run-
ning processes. To refer to the process you want to renice, use the -p option.
8. B. Explanation: mkill is not a current command to send signals to processes.
10 Red Hat RHCSA/RHCE 7 Cert Guide
9. A. Explanation: The SIGKILL signal sends the famous signal with number 9
to a process, which forces the process to stop.
10. A. Explanation: To change the process priority from top, use r for renice.
Chapter 10
1. B. Explanation: KVM virtual machines run directly on top of the KVM hyper-
visor module and are not depended on the availability of the management
program.
2. B. Explanation: The libvirtd process provides the management interface to
access KVM virtual machines.
3. A. Explanation: Hardware virtualization support needs to be present in your
computer hardware. If it is not you cannot use KVM virtualization. On some
computers, the feature is available, but not switched on by default. Switch it on
through your computer BIOS setup.
4. C and D. Explanation: Look for the vmx flag in /proc/cpuinfo to verify the
availability of hardware virtualization support or for the svm flag (for AMD
cpus). The lscpu command shows the hypervisor mode a host is offering, and
if used on a virtual machine it shows which type of virtualization platform this
machine is used on.
5. A. Explanation: The modprobe kvm command loads the KVM kernel module
and all its dependencies. Do not use insmod kvm; that command will not load
the kernel module dependencies as well.
6. C. Explanation: The virtual machine disk files by default are stored in /var/lib/
libvirt/images.
7. D. Explanation: Virtual machine configuration files by default are stored in
the directory/etc/libvirt/qemu.
8. C. Explanation: Automatic virtual machine startup can be enabled easily using
the Virtual Machine Manager Boot options interface.
9. C. Explanation: The virsh list command lists all virtual machines. Add --all to
also show virtual machines that are not currently active.
10. D. Explanation: The virsh destroy command is like pulling the power plug. It
halts a virtual machine immediately with all the possible bad consequences of
that.
Appendix A: Answers to the “Do I Know This Already” Quizzes and “Review Questions” 11
Chapter 11
1. D. Explanation: The gpgcheck= line indicates whether to check the integrity
of packages in the repository using a GPG key. Although useful, this is not
mandatory.
2. B. Explanation: If an RHEL system is not registered with RHEL, no reposito-
ries are available.
3. C. Explanation: Use baseurl to specify which URL to use. If the URL is based
on the local file system, it uses the URI file:// followed by the path on the
local file system, which in this case is /repo, which explains why there are three
slashes in the baseurl.
4. D. Explanation: GPG package signing is used to set a checksum on packages,
so that altered packages can easily be recognized. The main purpose of signing
packages is to make it easy to protect packages on internet repositories. For
internal repositories that cannot be accessed by Internet users, the need to add
GPG package signatures is less urgent.
5. D. Explanation: Both the commands “yum provides and yum whatprovides
can be used to search for files within a specific package. The file pattern must
be specified as */filename or as a full path, which is why answer D is the only
correct answer. Without the */ in front of the file name, you may get a match
that is based on the package description, not on the filename.
6. C. Explanation: The yum list all command shows installed packages and
packages that are available in the repositories. The question was how to show
installed packages (not all packages), which is why answer C is the correct
answer.
7. D. Explanation: The yum history command reads the /var/log/yum.log file
and shows recent yum history. In this list, every event is marked with a history
number that can be used with the yum history undo command.
8. A. Explanation: The yum install command installs individually downloaded
RPM files while looking for package dependencies in the current repositories.
This is better than using rpm -ivh, which does not consider the yum reposi-
tories. In earlier versions of RHEL, the yum localinstall command was used
to install packages that were downloaded to the local file system, but this com-
mand is now deprecated.
9. C. Explanation: Use the rpm -qf command to find which RPM package a spe-
cific file comes from.
10. C. Explanation: The --scripts option checks whether there are scripts in an
RPM package. If you want to query the package file and not the database of
installed RPMs, you need to add the -p option to the -q option, which is used
to perform RPM queries.